Imports System.Windows.Input

Namespace WPF.Commands
    ''' <summary>
    ''' Command for executing lambda expressions. Similar to the delegate command.
    ''' </summary>
    ''' <remarks></remarks>
    Public Class LambdaCommand
        Implements ICommand

        Public Property CanExecuteLambda As Func(Of Object, Boolean)
        Public Property ExecuteLambda As Action(Of Object)

        Public Property Caption As String

        ''' <summary>
        ''' Initializes a new instance of the <see cref="LambdaCommand" /> class.
        ''' </summary>
        ''' <param name="caption">The caption.</param>
        ''' <param name="canExecuteLambda">The can execute lambda.</param>
        ''' <param name="executeLambda">The execute lambda.</param>
        ''' <remarks></remarks>
        Public Sub New(ByVal caption As String, ByVal canExecuteLambda As Func(Of Object, Boolean), ByVal executeLambda As Action(Of Object))
            Me.Caption = caption
            Me.CanExecuteLambda = canExecuteLambda
            Me.ExecuteLambda = executeLambda
        End Sub

        ''' <summary>
        ''' Defines the method that determines whether the command can execute in its current state.
        ''' </summary>
        ''' <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
        ''' <returns>true if this command can be executed; otherwise, false.</returns>
        ''' <remarks></remarks>
        Public Function CanExecute(ByVal parameter As Object) As Boolean Implements System.Windows.Input.ICommand.CanExecute
            Return Me.CanExecuteLambda.Invoke(parameter)
        End Function

        ''' <summary>
        ''' Occurs when changes occur that affect whether or not the command should execute.
        ''' </summary>
        ''' <remarks></remarks>
        Public Event CanExecuteChanged(ByVal sender As Object, ByVal e As System.EventArgs) Implements System.Windows.Input.ICommand.CanExecuteChanged

        ''' <summary>
        ''' Defines the method to be called when the command is invoked.
        ''' </summary>
        ''' <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
        ''' <remarks></remarks>
        Public Sub Execute(ByVal parameter As Object) Implements System.Windows.Input.ICommand.Execute
            Me.ExecuteLambda.Invoke(parameter)
        End Sub

        ''' <summary>
        ''' Called when [can execute changed].
        ''' </summary>
        ''' <remarks></remarks>
        Public Sub OnCanExecuteChanged()
            RaiseEvent CanExecuteChanged(Me, EventArgs.Empty)
        End Sub
    End Class
End Namespace

using System.Windows.Interactivity;
    using System.Windows.Controls;
    using System.Windows;
    using System.Windows.Input;
    using System.Windows.Data;
    /// <summary>
    /// Associate this behaviour with the button that you mark as IsDefault
    /// to trigger the ViewModel update when the user clicks enter in a textbox
    /// and the property doesn't update because the update source is set to
    /// lost focus.
    /// </summary>
    public class DefaultButtonUpdateTextBoxBindingBehavior : Behavior<Button>
    {
        /// <summary>
        /// Hook into the button click event.
        /// </summary>
        protected override void OnAttached()
        {
            AssociatedObject.Click += AssociatedObject_Click;
            base.OnAttached();
        }

        /// <summary>
        /// Unhook the button click event.
        /// </summary>
        protected override void OnDetaching()
        {
            AssociatedObject.Click -= AssociatedObject_Click;
        }

        /// <summary>
        /// The click event handler.
        /// </summary>
        void AssociatedObject_Click(object sender, System.Windows.RoutedEventArgs e)
        {
            // Get the element with the keyboard focus
            FrameworkElement el = Keyboard.FocusedElement as FrameworkElement;
            if (el != null && el is TextBox)
            {
                // Get the binding expression associated with the text property
                // for this element.
                BindingExpression expression = el.GetBindingExpression(TextBox.TextProperty);
                if (expression != null)
                {
                    // Now, trigger the update.
                    expression.UpdateSource();
                }
            }
        }
    }